The systems and techniques described herein were made in the performance of work under a NASA contract, and are subject to the provisions of Public Law 96-517 (35 USC 202) in which the Contractor has elected to retain title.
This application relates to modulation of optical signals, and more specifically, to methods and devices for modulating an optical signal by using electro-optical modulators.
Optical communication systems use one or more optical carrier waves to provide high-speed and wide bandwidth signal transmission. An optical carrier wave can be transmitted either through the free space or in an optical waveguiding channel such as a fiber link. The data capacity of a fiber link can be increased by using a wavelength-division multiplexing technique which simultaneously transmits optical carriers of different wavelengths over the same fiber so that different channels of data can be sent at the same time. Many other non-optical communication systems, such as wired networks, radio wireless networks, satellite communication systems, can be combined with optical systems to meet various communication needs and requirements.
An optical communication system may include a light source such as a laser to produce the optical carrier wave, an optical modulator to modulate the optical carrier wave to carry information, and an optical receiver which may include a photodetector to convert the optical information into a desired electronic format for further processing. The optical modulator may modulate either the phase or amplitude of the optical carrier wave. It is desirable to obtain high energy efficiency and a high modulation speed in an optical modulator for optical communication and other applications.
The present techniques and devices for optical modulation include an electro-optic light modulators formed from gallery-whispering-mode resonators. One embodiment of such a modulator includes a gallery-whispering-mode resonator formed of an electro-optical material, a first optical coupler to couple an input laser beam into the resonator, a second optical coupler to couple the optical energy out of the resonator to produce an optical output, and an electrical coupler to apply a driving electrical signal. The optical energy from the input laser beam is coupled to into the resonator in one of the whispering gallery modes. The applied electrical signal modulates the dielectric constant of the resonator and hence the mode of the whispering gallery modes. This modulates the intensity of the output from the second optical coupler.
One configuration of various forms of the gallery-whispering-mode resonator may be a disk-like resonator formed around an equator of a sphere.